as the topic says.
polyphoni on instruments work fine with computer keyboard, but not when recording notes in with midi.
i use a behringer umx 61 midi controller.
it works fine in sonar 7.
I’m sure you are overlooking something as there is no problems here with polyphonic key-transitions across midi.
Let’s follow a few basic questions from the list when this issue pops up and see if you can answer any of these in a somewhat positive manner that leads to a solution:
Did you actually have the selected instrument filled with any content? (samples / plugin / midi channel).
No assignment leads to a non-qualified instrument (at which Renoise ignores polyphonic input)
Did you toggled the “Chord” button? If it is turned off, polyphonic mode is turned off.
If you do see multiple notes in the track, but your instrument refuses to play simultaneous notes, your instrument does not support polyphonic notes or it is disabled somehow (inside your plugin or midi device)…
Could i have forgotten some other option?
yes
Ooooops!!! no 
sorry for this lameness
i was also sure i had it working previously…
thanks vincent
This already confused so many people. I think we should trash this option as soon as possible.
There should be an instrument setting to make the insturment polyphon/monophon and not the input.
That sounds more natural indeed.
At least we know for sure that polyphonic troubles can only be corrected through the instrument settings and nowhere else. Besides that, we have then a spot open in the controlpanel for another (confusing) button.